Ya know, I think it was at SakuraCon a few years ago... I recall there being a wedding (which counted as a real one as the person officiating was legally registered to do so) as the "halftime show" for cosplay. It was Mark [the MC] who got married. They'd turned the whole thing into an amusing act -- the bride walked in to the Darth Vader theme.
Yes, you can do a cosplay themed wedding and could theoretically do it at a convention. The only thing I'd recommend is that you set up some sort of small Mundane ceremony for the parental units who'll freak out about the "odd" wedding. I've seen weddings at SCA events where all attendees are dressed in medieval clothing. If you do want to arrange your wedding you could have it as a "panel" during the convention...witnesses would turn out to be any and all con attendees who chose to show up for it. As for getting someone to officiate, there are various people in fandom who are legally able to marry people and who would be happy to perform the ceremony. (in fact, there's even a Roman Catholic priest somewhere in California -- last saw him at Mass at CascadiaCon -- who goes to conventions just 'cuz he enjoys them, and of course he would say Mass and do a wedding ceremony if asked.... don't recall his name, but might be able to look it up if you want him to perform the ceremony. ) One thing to note would be that wedding attendees would have to be registered convention attendees -- unless you just did it at an area nearby the convention.
